BF109 Engine Damage in boost/emergency mode

[ZachariasX]

by the end of the war, C3 fuel was either the rough equivalent of 95/130 or 97/130. Allied 100/150 was actually closer to 110/150, so the octane rating of U.S./U.K. Avgas was always higher.

 

its not hard to figure out why, German fuel was made from coal which had a lower natural octane rating than petroleum as well as other performance issues. If the Germans had unlimited time and unlimited access to strategic raw materials, they might have been able to produce an equivalent fuel, but they didn't so had to make to with what they had.

 

it's no hard to see that German coal based synthetic fuels did not perform as well.

 

The Germans were running the FW190 A8 with a maximum boost of 1.65 ata in 44-45. 1.65 ata is the equivalent of +49" hg.

 

so you have an engine (BMW 801) with a base compression ratio of 6.5:1 with a max. boost of +49" hg. giving you a max compression ratio of roughly 10.7:1.

 

late war P51s were running with a boost of +75" hg.

 

so you have an engine (Merlin) with a base compression ratio of 6:1 with a max. boost of +75" hg. giving you a max compression ratio of roughly 15:1.

 

of course, octane rating is just one parameter, there were many other design differences as well between the two engine setup.

It is irrelevant wheter you have synthetic fuel or fossil fuel. The fossil fuel gave just good quality „base fuel“ (without aromatic compound or lead added) by simple refining procedure. If you have to make synthetic fuel from coal, that is just more effort. If you couldn‘t do that, nobody would mine the oil sands to get fuels from that. By now, most liquid oil ressources have been pumped dry, and we are going after any sort of fossilized carbon, even if it comes at great cost and pollution, but you get all the fany fuel that you want.

 

You also have to consider that German fuels are not primarily „bad“ at rich mixture ratings, but lean mixture rating. This means that your great high perforimg fuel is not readily digested on endurance flights.

 

In principle, you cannot go past 100 octane in your „base fuel“, this only should you be lucky enough to have pure isooctane at hand. Add TEL, you get maybe 120 at the most.

 

This means a great portion of your fuel (sometimes more than half of it) is aromatic compounds. These fuels parts do not burn as clean as isooctane, reducing effective power output and add engine trouble.

 

So in essence you are facing just a more elaborate trade off between ease of production, efficiency and max power production. The allies just had a head start of about 15 octane ratings in their base fuel. This matters a lot. The 100/145 grade allied fuel was mostly sythetic as well. And it was effectively a dud, discontinued for a reason. You don‘t get such ratings with isooctane.

Edited January 27, 2018 by ZachariasX

[JtD]

There's not free lunch in chemistry, is there.

 

I don't know if it was mentioned already, according to Jumo fuel specifications, Bleitetraäthyl content was specified 0.115-0.120% for both C3 and B4, giving octane ratings of >95 and >89 respectively.

[Panthera]

Sgt_Joch it seems you did not read the link provided because the German did infact later add more isoparaffin and ended up with fuel equal to the Allied 150 grade.

 

It all depends on which type C3 was tested

, the Germans obviously not being able to supply as steady a stream of this higher quality fuel as they would've wanted. Even B4 was in desperate short supply.

Edited January 27, 2018 by Panthera

[ZachariasX]

Sgt_Joch it seems you did not read the link provided because the German did infact later add more isoparaffin and ended up with fuel equal to the Allied 150 grade.

It all depends on which type C3 was tested

, the Germans obviously not being able to supply as steady a stream of this higher quality fuel as they would've wanted. Even B4 was in desperate short supply.

High octane rating doesn‘t mean automatically that it is good fuel. It just is a statement about (pre)detonation, especially since you are passing „100“, where octane rating is absurd per se, as you cannot get purer as pure isooctane. That you implicitly correlate that with burn properties beyond that should tell you that this is a very indirect, although useful, tool to describe your fuel.

 

Funny enough that supposedly „150% pure“ isooctane contains in fact less than 50% isooctane should get one thinking.

 

If predetonation is your only concern, you can put diesel in your engine. It would have a very high octane rating besides the fact that it hasn‘t one.

 

On average, there has never been better fuel for a Merlin than 100LL Avgas. You have to go great lenght to get higher performing fuels. Stuff they use for Reno Air Races. Check out also the price for a can.

[Panthera]

High octane rating doesn‘t mean automatically that it is good fuel. It just is a statement about (pre)detonation, especially since you are passing „100“, where octane rating is absurd per se, as you cannot get purer as pure isooctane. That you implicitly correlate that with burn properties beyond that should tell you that this is a very indirect, although useful, tool to describe your fuel.

 

Funny enough that supposedly „150% pure“ isooctane contains in fact less than 50% isooctane should get one thinking.

 

If predetonation is your only concern, you can put diesel in your engine. It would have a very high octane rating besides the fact that it hasn‘t one.

 

On average, there has never been better fuel for a Merlin than 100LL Avgas. You have to go great lenght to get higher performing fuels. Stuff they use for Reno Air Races. Check out also the price for a can.

 

Well it obviously depends on what the engine is designed for as well, the Merlin from the start being designed for natural derived fuel with a high base octane value whilst the German engines were designed to run on synthetic fuels, most of which was 87 octane.

 

As a result of good engineering the Allies & Germans were in a close race HP rating wise from start to finish.

[JtD]

The early Merlins ran on 87 octane fuel, just like the DB601. 87 octane was pretty much mid 1930ies standard rating for high performance aviation fuel. All nations used leaded oil based fuel and designed their newest engines for fuels around 87 octane back then.

 

It wasn't until the second half of the 30ies that the Nazi government put a large emphasis on using internal German resources that they started replacing oil with coal based aviation fuel. Which then of course had to be a suitable replacement, still usable with modern high performance engines, and needed to also be 87 octane.

[ZachariasX]

Well it obviously depends on what the engine is designed for as well, the Merlin from the start being designed for natural derived fuel with a high base octane value whilst the German engines were designed to run on synthetic fuels, most of which was 87 octane.

 

As a result of good engineering the Allies & Germans were in a close race HP rating wise from start to finish.

You don‘t design engines for natural or synthetic fuel. You design it either for octane fuel or diesel or whatever. Boiling point etc. are standards that have to be mainained regardlss of what liquid you burn in that engine, as they define what „gasoline“ is, not octane rating.

 

Octane rating comes only in play if you start to incrase compression. Otherwise, the burn efficiency will affect the mileage you can get from your engine.

 

It is true, as you say, that „the German recipe“ did roughly enable similar compression rates (eventually), but if it doesn‘t burn as efficient, you will have less range. Lean mixture rating is very important, as the plane will spend most of it hours in that regime. It means increased service requied for the engine to clean it and flat out increased range from the same barrel.

 

How bad these fuels were (even allied ones) you can see when you put modern avgas in these planes and see how nicely these engines can run.

 

Especially the „simple“ engines love the new fuels. Put in V-Power in a old motorbike with a two stroke engine. That quickly puts an end to stalling on red lights. In modern cars, it is less of an issue as modern injector engines just use what they need for desired power output. Still, better fuel will keep your engine cleaner and you potentially have more mileage, depending on your driving style.

 

If you really want power from your engine, use nitromethane. (If you can steal it from somewhere, they don‘t sell it anymore just like that). Same as those high power fuels, it has nothing to do with octane, but boy, you can fire up your engine...

[MiloMorai]

Read somewhere that the 100 octane avgas used extensively by RAF FC during the BoB was actually 100/130 fuel.

 

Anyone come across this before?

[ZachariasX]

Read somewhere that the 100 octane avgas used extensively by RAF FC during the BoB was actually 100/130 fuel.

 

Anyone come across this before?

If nothing else is stated, AFAIK you state the lean mixture rating. Soit would be something like 100/130, depending on the amount of TEL added. Thus, Avgas 100LL is in fact 100/130 stuff. They were just lucky that the juice that spilled from the holes in the desert gave them 87 octane without doing much to it. Adding TEL menat you get 100 octane.

 

As both Allies and Axis constantly keept cooking new recipies for fuel, we can expect that there are mild changes in true ratings, if you were intrepid enough to go and meter a sample from a barrel that filled your Spit.

 

To get a better understanding of the German predicament when it came to design their own engines (like the DB 60X) after having Kestrel (etc.) engines, you have to be aware of the fact that making a new engine block for Daimler et. al. meant an investment in the coming decade. The last thing you do at this point is speculate about things that you would like them to be. You have what you have. Engine blocks are here to stay for half a century if things go as they (economically) should.

 

They knew they would have to rely on their own fuel, and they knew that making a very high quality fuel was not economically viable in the large scale. So, back in the thirties, they needed to design an engine that would accept poorer fuel quality without much issues regarding service life. And I guess it cannot be disputed, that the DB-60x series were a very, very good design if you look what fuel they had at hand when they came up with that one. It is an engine that in principle can be run on low rated fuels, something that wouldn't realy "fly" with Merlins. As for maximum power, there was never a real problem at all, as on average German engines were very much on par with anyone else regarding max. power output.

 

What changed over time is that the Germans really had to up compression to the levels of the Aliies to get all they could from the engines in times of sheer desparation. This is however a rather different time compared to up to 1940, where the Übermensch was still confident to conquer the world, well, just because.

 

The whole fuel situation was a real issue just before the war and early in the war, where the Aliies always could build engines suitable for higher grade fuels. Later in the war, who cared about efficiency or service life, when you didn't have to fly far anymore to get killed. And yes, they didn't have enough of it, but that comes along with losing a war. Then, they really tried everything to get their soup up to 150 octane, at any costs, as the Allies did with very mixed results.

[Sgt_Joch]

one way the Germans partially solved the performance gap/low octane dilemma was by using engines with a larger displacement, i.e. 41 liters for the BMW801, 35 liters for the DB605 vs 27 liters for the Merlin.

 

but that runs into the other problem that your engines will tend to be larger and heavier which has an impact on aircraft design.

Edited January 28, 2018 by Sgt_Joch

[MiloMorai]

The Brits changed the way they stated what octane their fuel was?

 

DB601 was 6.9:1 cr when early Merlins were 6:1 cr.

[ZachariasX]

The Brits changed the way they stated what octane their fuel was?

 

DB601 was 6.9:1 cr when early Merlins were 6:1 cr.

The Merlin was designed 1935. By that time, it as unusual to have laded fuels. Hence the block was designed. What hey did do as soon as TEL became commodity, is to add compression by means of the turbochager. The great thing about the Merlin was in fact the turbocharger, most notably in form of the two stage, two gear kind in the 60s series.

 

Knowledge in producing good radial compressors made the later gas turbines (Ghost, Nene) such great engines.

[Talisman]

Hi Folks,

 

Re the Merlin and 100 Octane fuel.  Some interesting extracts and links to web pages below: 

 

 

In 1939 a decision was made to focus on 100 octane fuel for aero engines. This fuel permitted higher boost pressures and temperatures without detonation, and allowed the use of +12lb boost rather than the previous limit of +6lb.

http://www.hurricane501.co.uk/2015/10/15/the-rolls-royce-merlin-aero-engine-hawker-hurricane-supermarine-spitfire-dehavilland-mosquito-avro-lancaster-p51-mustang/

 

The Rolls Royce engineers were told that a higher octane fuel was
being developed, and modified the Merlin to make use of it by revising
the amount of fuel and air that got packed into the intake manifold.
They could do this because they knew that the higher octane fuel would
resist detonation that would otherwise have occured with the higher
manifold pressures being run in the engine. They managed this in
large part by revising the supercharger, allowing it to increase it's
compression ratio.

http://soc.history.war.world-war-ii.narkive.com/5vmxISul/100-octane

 

Happy landings,

 

56RAF_Talisman

[ZachariasX]

Hi Folks,

 

Re the Merlin and 100 Octane fuel.  Some interesting extracts and links to web pages below: 

 

 

In 1939 a decision was made to focus on 100 octane fuel for aero engines. This fuel permitted higher boost pressures and temperatures without detonation, and allowed the use of +12lb boost rather than the previous limit of +6lb.

http://www.hurricane501.co.uk/2015/10/15/the-rolls-royce-merlin-aero-engine-hawker-hurricane-supermarine-spitfire-dehavilland-mosquito-avro-lancaster-p51-mustang/

 

The Rolls Royce engineers were told that a higher octane fuel was[/size]being developed, and modified the Merlin to make use of it by revising[/size]the amount of fuel and air that got packed into the intake manifold.[/size]They could do this because they knew that the higher octane fuel would[/size]resist detonation that would otherwise have occured with the higher[/size]manifold pressures being run in the engine. They managed this in[/size]large part by revising the supercharger, allowing it to increase it's[/size]compression ratio.[/size]

http://soc.history.war.world-war-ii.narkive.com/5vmxISul/100-octane

 

Happy landings,

 

56RAF_Talisman

You can see this in context of the German continued efforts to increase displacement, not counting on increasing compression for efficientcy purposes.

 

If the Merlin wasn‘t easily cropped that way, I would guess there would have been a lot more Griffons sooner. But it woukd have meant dusruptins in production and assembly lines.

[Panthera]

one way the Germans partially solved the performance gap/low octane dilemma was by using engines with a larger displacement, i.e. 41 liters for the BMW801, 35 liters for the DB605 vs 27 liters for the Merlin.

 

but that runs into the other problem that your engines will tend to be larger and heavier which has an impact on aircraft design.

AFAIK the DB60x series is actually smaller than the Merlin, a good visual example of this is how much the nose grew on the spanish 109 Buchons which had the Merlin engine instead.

 

On another note IIRC the next German engines to come had the war lasted a little longer would've had 4 valves pr. cylinder, which would've added quite abit of extra power for any fuel used.

Edited January 29, 2018 by Panthera

[Sgt_Joch]

Sgt_Joch it seems you did not read the link provided because the German did infact later add more isoparaffin and ended up with fuel equal to the Allied 150 grade.

 

 

 

why yes I did read it Panthera and I rejected it because  it only makes a general statement, but links to no source to support its conclusions.

 

Actual testing by the British during the war and postwar by the USSBS showed a octane rating of 95-97/130.

[Sgt_Joch]

AFAIK the DB60x series is actually smaller than the Merlin, a good visual example of this is how much the nose grew on the spanish 109 Buchons which had the Merlin engine instead.

 

 

 

 

I said "tend" as a general statement, the BMW801 and Jumo 213 were both heavier than say the Merlin or the Allison.

 

Normally for a given displacement, you want to have an engine block of a certain size and weight. You can try to squeeze more displacement out of a smaller block, but you can quickly run into durability and reliability issues.

 

 

 

On another note IIRC the next German engines to come had the war lasted a little longer would've had 4 valves pr. cylinder, which would've added quite abit of extra power for any fuel used. 

 

The Merlin, Allison and certain German engines, like the DB605, already used 4 valves per cylinder. 4 valves  only allows you to have greater fuel flow at higher RPM. It does not solve the low octane equation.

[Panthera]

I said "tend" as a general statement, the BMW801 and Jumo 213 were both heavier than say the Merlin or the Allison.

 

Normally for a given displacement, you want to have an engine block of a certain size and weight. You can try to squeeze more displacement out of a smaller block, but you can quickly run into durability and reliability issues.

 

 

The Merlin, Allison and certain German engines, like the DB605, already used 4 valves per cylinder. 4 valves only allows you to have greater fuel flow at higher RPM. It does not solve the low octane equation.

The Jumo 213 was heavier than the Merlin or Allison yes, but also generated a lot more base HP, 1,750 PS on B4 and 2,000 PS on C3 (B model). The BMW 801D radial was similar to the P&W R-2800 in output & size, the last model (801F) producing 2400 hp at take off power, with water methanol it could've potentially hit over 3,000 PS.

 

The Jumo 213 was the engine which I read went from 1,750 PS take off power to 2,380 PS by going with four valves instead of three, now I remember, a rather hefty increase of 630 PS.

 

As for the effect of more valves, it allows for higher volumetric efficiency, at least to a point.

Edited January 29, 2018 by Panthera

[Dakpilot]

The Jumo 213 was heavier than the Merlin or Allison yes, but also generated a lot more base HP, 1,750 PS on B4 and 2,000 PS on C3 (B model). The BMW 801D radial was similar to the P&W R-2800 in output & size, the last model (801F) producing 2400 hp at take off power, with water methanol it could've potentially hit over 3,000 PS.

 

The Jumo 213 was the engine which I read went from 1,750 PS take off power to 2,380 PS by going with four valves instead of three, now I remember, a rather hefty increase of 630 PS.

 

Jumo 213 was 35 litre engine, Allison and Merlin are 28-27 litre

 

you would probably be better off comparing with Griffon with its closer displacement when considering 'base' HP

 

Not certain that the increase of 630 PS could be so simply put down to 4V over 3V's, and 213J was rather more of a theoretical design than a production engine, but a 4V head would certainly have helped with volumetric efficiency at the (comparatively) quite high rev's that 213 operated at, especially when compared to the 211 it was based on (40% RPM increase)

 

Also although Jumo 213 was a development of Jumo 211 it was a newer design engine when introduced in 42/3 (first flight in 41)

 

Cheers, Dakpilot

[Panthera]

Jumo 213 was 35 litre engine, Allison and Merlin are 28-27 litre

 

you would probably be better off comparing with Griffon with its closer displacement when considering 'base' HP

 

I was talking actual physical size and weight, not displacement as here the Germans tended to use bigger cylinders, even the DB60x series which was physically smaller than the Merlin had a much larger displacement.

 

Not certain that the increase of 630 PS could be so simply put down to 4V over 3V's, and 213J was rather more of a theoretical design than a production engine, but a 4V head would certainly have helped with volumetric efficiency at the (comparatively) quite high rev's that 213 operated at, especially when compared to the 211 it was based on (40% RPM increase)

 

Also although Jumo 213 was a development of Jumo 211 it was a newer design engine when introduced in 42/3 (first flight in 41)

 

Cheers, Dakpilot

The 213J was produced and bench tested AFAIK, however the war ended before full scale production could ensue. Edited January 29, 2018 by Panthera

[Dakpilot]

I don't think a DB 605 is much smaller than a Merlin, about 2 or 3 inches and about an inch on an Allison as far as length and very similar in other respects

 

Cheers, Dakpilot

[Panthera]

I don't think a DB 605 is much smaller than a Merlin, about 2 or 3 inches and about an inch on an Allison as far as length and very similar in other respects

 

Cheers, Dakpilot

 

Oh I agree, it wasn't by much, however still noteworthy considering the difference in displacement. Weight was within 10 kg of each other, the DB was just a smidge more compact.

 

I'd say the biggest advantage of the DB was the lower placement of the exhausts which resulted in much reduced noise in the cockpit.

[Panthera]

A Jumo 213J performance chart:

[Dakpilot]

Whilst the Jumo 213J potentially had the chance to be a very high performance engine there were many issues that would have had to be solved for it to be produced, at 3700rpm with increased displacement over 213A it was approaching piston speeds of 21 m/s that were way higher than any comparative engine and with piston and crank journal loads up to double that of any previous engine produced

 

The 2 stage 3 speed supercharging and new cooling system were also untested, the very few bench tests showed alarming wear, it really should be considered as a what if prototype

 

The charts above are projected performance not actual

 

Cheers, Dakpilot

[Panthera]

Whilst the Jumo 213J potentially had the chance to be a very high performance engine there were many issues that would have had to be solved for it to be produced, at 3700rpm with increased displacement over 213A it was approaching piston speeds of 21 m/s that were way higher than any comparative engine and with piston and crank journal loads up to double that of any previous engine produced

 

The 2 stage 3 speed supercharging and new cooling system were also untested, the very few bench tests showed alarming wear, it really should be considered as a what if prototype

 

The charts above are projected performance not actual

 

Cheers, Dakpilot

 

Yes actual bench tested performance was higher by about 90 hp it seems. As for the accelerated wear, yes that is unavoidable with higher rpms. 

 

Anyway it is a good indicator of what was on the way had the war taken a different turn, with similar increases in power already being achieved with the BMW 801. 

 

The problem in the end for the Germans was the lack of time & resources, not to mention free space/peace of mind without having to constantly get interrupted by bombing raids, to get all these new engines into production. 

 

Btw it's quite interesting to note how high a performance the Japanese managed to squeeze out of their engines despite having to use probably the lowest octane fuel of any combatant during the war:  Up to 2,050 hp from the 810 kg Ha-45 engine powering their Ki-84 & N1K2J fighters.

Edited January 29, 2018 by Panthera

[1stCL/Werner]

Just run across this interesting picture of F cockpit. Note that label on dashboard  showing 3 mins for 2750 RPM.

[unreasonable]

That is interesting - also on the speedometer there are numbers which are what?  Maybe dive speed limits at different heights in km? The boost pressure gauge looks customized too.

 

Actually a good way to mark up a cockpit: wish we had mods-on mode so I could do it in mine. What with all the swapping aircraft I tend to do I am constantly forgetting the limits. ;(   

 

 

BTW That is an E cockpit according to the only site I can find that has it: image 47 from  https://www.worldwarphotos.info/gallery/germany/aircrafts-2/messerschmitt-bf-109/bf109-e-6-jg-53-cockpit-40/

 

edit: but the dials look like an F for sure so that is odd.

Edited February 16, 2018 by unreasonable

[1stCL/Werner]

It's not E cockpit for sure.

 

Yes marks around speedometer are max speed in altitudes, but that was quite common.

Boost pressure gauge is just another type, more common in later years of war.

[Kurfurst]

I'd say that is pretty convincing evidence for the actual time limits on the DB 601E / Bf 109F-4 (given the 2700 rpm marking). Great work Werner! 

 

For the F-2 with 601N, it appears the "time limit" was also 3 minutes - see paragraph 4 on the sixth page of this manual. 

 

"... der Start- und Notleistung aus eine Dauer von 3 Minuten begrenzt ist."

 

http://www.kurfurst.org/Performance_tests/109F1F2_Kennblatt/Kennblatt_fur_Bf109F1F2_DB601N.PDF

Edited February 16, 2018 by VO101Kurfurst

[Sgt_Joch]

emergency power on the F2 in game, i.e. up to 2800 rpm is already 3 minutes. What am I missing?

[-=PHX=-SuperEtendard]

For the F-2 in game it's Emergency Mode at 1.35 ata 2600 RPM as 3 minutes and Boosted mode as 1.42 ata at 2800 RPM for 1 minute.


For the F-4, at 1.37 ata at 2600 RPM is around 4 mins I think, with up to 9 mins if you are lucky. 1.42 ata 2700 RPM is 1 min.

Will test 2750 RPM and see how it goes.

Edited February 17, 2018 by -=PHX=-SuperEtendard

[Sgt_Joch]

Is the photo from an F2 or an F4?

 

will have to re-test, but I think if you go to 2750 rpm in a F2, you are still at emergency power.

Edited February 16, 2018 by Sgt_Joch

[Dakpilot]

I would say that gauge is marked at 2700 rpm 

 

there is quite a lot of parallax in the photo

 

Cheers, Dakpilot

[unreasonable]

I would say that gauge is marked at 2700 rpm 

 

there is quite a lot of parallax in the photo

 

Cheers, Dakpilot

 

I agree - it looks as though it is taken slightly to the left of the cockpit looking slightly right. So the rpm limit lines are probably meant to be at 2300, 2500 and 2700.

Edited February 17, 2018 by unreasonable

[1stCL/Werner]

Seems, that you're right. Than it could be F-4 with 1.42ata/2700rpm rating.

 

Photo from bivalov from another topic showing this:

(Walter Hagenah crashed with F-4  "yellow 4" in Vienna on 22. april 1942)

[=EXPEND=13SchwarzeHand]

It is definitely an F-4

 

http://www.luftwaffe.cz/hagenah.html

"On 22 April, the unit was ordered to relocate to Vienna-Aspern in preparation for service on the Eastern front. Hagenah suffered a take-off accident in Bf 109 F-4 “Yellow 4” at Vienna, fortunately without injury."

The caption says it a view into the cockpit of "Yellow 4".

 

I conclude these are the same.

 

Think that is pretty good evidence against the current specifications

 

Engine modes:
Nominal (unlimited time): 2300 RPM, 1.15 ata
Combat power (up to 30 minutes): 2500 RPM, 1.3 ata
Emergency power (up to 1 minute): 2700 RPM, 1.42 ata

 

should be 3 minutes.

Edited February 17, 2018 by =EXPEND=SchwarzeDreizehn

[Dakpilot]

All good info

 

however i would dispute it being "good evidence" against the current specs (however right or wrong)

 

What the pics show are a 3 minute limit at 2700 rpm painted on the dash/instrument by Pilot or ground crew, it is a little bit of a leap/assumption to apply this also to ATA and to all series DB601/F4 from a research point of view

 

 

Chris Starr dates the introduction of the 1.42ata capable Dw250ET 7/1 spark plug to the summer of 1943. This implies that whatever genuine results were obtained in the tests of an F-4 at Rechlin, these were not a realistic measure of what a combat pilot could achieve during the heyday of the aircraft, which was 1942. By the time Luftwaffe allowed its engines to be pushed this hard the F-4 had already passed from frontline service.

 

Chris Starr is a (fairly) well known aero engine expert ( helped rebuild 109G 'Black Six') and has written a number of articles on DB engines (none of which I now have unfortunately)

 

There are many examples of the 1.42 limit being banned at various time cycles on DB601/605 series engines and on multiple occasions for various reasons, but the main being detonation 

 

does anyone else have any info on spark plugs? it would seem to be confirmed that the standard Dw250ET 7 caused detonation at 1.42 ATA on 87 B4 fuel

 

but I am not informed enough to comment on the introduction times of various spark plug specs, with the later Bosch DW250ET 7/1A and 10/1 being applicable for 1.80 ATA and the Beru F280 E43 being introduced to cope with 1.98 ATA

 

Further info or refute/confirmation of the subject would be useful

 

Cheers Dakpilot

[Kurfurst]

All good info

 

however i would dispute it being "good evidence" against the current specs (however right or wrong)

 

What the pics show are a 3 minute limit at 2700 rpm painted on the dash/instrument by Pilot or ground crew, it is a little bit of a leap/assumption to apply this also to ATA and to all series DB601/F4 from a research point of view

 

 

Chris Starr dates the introduction of the 1.42ata capable Dw250ET 7/1 spark plug to the summer of 1943. This implies that whatever genuine results were obtained in the tests of an F-4 at Rechlin, these were not a realistic measure of what a combat pilot could achieve during the heyday of the aircraft, which was 1942. By the time Luftwaffe allowed its engines to be pushed this hard the F-4 had already passed from frontline service.

 

Chris Starr is a (fairly) well known aero engine expert ( helped rebuild 109G 'Black Six') and has written a number of articles on DB engines (none of which I now have unfortunately)

 

There are many examples of the 1.42 limit being banned at various time cycles on DB601/605 series engines and on multiple occasions for various reasons, but the main being detonation 

 

does anyone else have any info on spark plugs? it would seem to be confirmed that the standard Dw250ET 7 caused detonation at 1.42 ATA on 87 B4 fuel

 

but I am not informed enough to comment on the introduction times of various spark plug specs, with the later Bosch DW250ET 7/1A and 10/1 being applicable for 1.80 ATA and the Beru F280 E43 being introduced to cope with 1.98 ATA

 

Further info or refute/confirmation of the subject would be useful

 

Cheers Dakpilot

 

The qoute seems to come from a forum poster at Axishistory.com. I cannot say if its accurate, but from what I have, spark plugs were not a particular head ache. It is true that 1940s spark plugs had narrow temperature limits, and perhaps better plugs helped, but then why all the top brass never seem to discuss them?

 

In any case, for the DB 601E the manuals at the end of 1941 clear the 1,42ata rating, and various test were made in 1942 at the full rating. I doubt that the issue, whatever it was, persisted. M. Rausch properly summarized the available documentary evidence in that thread BTW.

 

 

 

"So the use of 1.30 ata in September 1941 and 1.42 ata in February 1942 are documented. Hence between October 1941 and January 1942 emergency boost was cleared for the DB 601 E. Since the JG 26 had to use a boost of 1.42 ata for their results, it is possible that the boost of 1.42 was permitted before December 1941. There is no documentation found till now, that after the DB 601 E was cleared for a boost of 1.42 ata it was later again reduced to 1.30 ata."

 

 

BTW, "detonation" was never a problem on the 605A. Why the 601E was initially restricted to 1,30ata I do not know, but it probably was a mechanical issue, not an ignition related one. AFAIK detonation became a problem in 1945 when sub-standard batches of B-4 started to deviate from the standard B-4 and pre-ignition and white flames were observed on the DB 605DB. The solution was to switch the engine to later ignition and thus reduce the compression ratio. However, the engine had no problem with operating on standard quality B-4,  that one was operating at 8.5:1 compression ratio and 1.45 ata (and at Startleistung, even allowed up to 1.5 ata w/o water injection), so even higher than the 605A (7.5:1, 1.42ata). If this shows you something, it is that the standard B-4 still had quite a bit of  anti-detonation reserves compared to what it used for on the 605A.

 

As for the 605A, the "burnt through pistons" was not a serious issue either, as already at the time of its service introduction (June 1942) the telegram mentioning the blocking of 1,42ata already mentions and makes it clear that a stronger piston crown was being fitted to the engines. The new piston heads are shown as mods in the more technical DB 605A manuals that even show cut sections. The 605A's main issue were related lubrication of the new bearings. The new engine had plain bearings instead of the rolled bearings (probably due to better availability), and in addition, a larger capacity oil pump that caused bubbles in the lubrication, and when coupled with higher stresses from higher powers and revs, the results are easy to predict - the bearings simply could not take the load as they did not have proper lubrication. There was also some finger pointing between DB and Mtt about whether the latter's actual execution of the oil system (oil pressure) satisfied DB's specs for the engines (DB complained that the oil pressure is too low). This was perhaps true as well but not as much of a major issue either, as the whole problem appears to be solved in the late summer of 1943 when they have successfully tested and then re-fitted oil de-aerators, allowing for the clearance of 1.42ata on the 605A, and very shortly afterwards, 1.7ata with MW injection.

[Dakpilot]

The qoute seems to come from a forum poster at Axishistory.com. 

 

The quote is about the 6 page article by Chris Starr 'Developing power' - Daimler Benz wartime efforts to increase power in DB600 series engines,  published May 2005 Aeroplane Monthly

 

who M. Rausch is or what his credentials are I have no idea

 

You say burnt through pistons on DB 605 and at the same time that detonation was never an issue? how do pistons burn through without detonation?

 

You also say that the oil problem was not much of a major issue yet it took over 1 year from introduction as combat engine - June 42 to late summer 43 for 1.42 to be cleared for operational use, a critical period (before widespread mass bombing disrupted German aviation production)  when this would have been rather useful to pilots on the front, ...the issue being cleared up shortly after the claim made that improved spark plugs became available...

 

The improved ATA rating available would also seem to be tied to the improvements in spark plug design as they also became available rather than suggesting the "standard B-4 (87 oct) fuel still had quite a bit of anti detonation reserves compared to what it used for on DB605" ?

 

I would have thought that having to suffer a de-rated engine in combat for more than a year would have led to some "discussion from top brass" Daimler Benz were not a small or backward operation..far from it.

 

I find it hard to just brush off this point so quickly, which is why I asked if anyone had more info on the article or it's content (it is also quoted in at least some books) as it points to hard facts rather than 'interpretation' of test flights

 

Cheers Dakpilot

[303_Bies]

My two cents. 

I'm mostly "Russian pilot" at the game, but i follow all this discussion about strict limitations for DB601 or BMW801.

 

I can say one thing: we should find some compromise because in real life it was obviously very different. Soviet airplanes (especially in period depicted at the game 1941-1943) rarely met this official parameters in any regard. Mother Russia was fighting for her life with every possible mean, her aircrafts was often produced by unqualified staff, woman and children in hastily assembled plants. Often without any proper quality control. Many Russian aircrafts reached different parameters even between the same batch from the same factory. Quality of their engines and airframes was very low and varied greatly and many of them was being sent to the units directly from factory - sometimes even with incomplete equipement - just to stop the nazi. The engines lost oil, fouled, leaked, the surface of the wooden panels detached at higher speeds, airframes wasn't plain, some parts of equipement were missing etc.

 

At the same time Germany had the comfort of having very high quality standards before allied bombardment, every engine, every airframe was thoroughly tested and only after that qualified for use and send for line units.

 

In real life, early in the war, in many cases Klimov 105 failed faster on nominal parameters regime than DB601 on combat power... Many Russian aircrafts from this period was forced to turn back just after the start because of engines malfunctions etc. Failures of defected aircrafts caused as many fatal accidents in VVS as fight against Germans. That was the reason some Russian veterans prefered fo flight older western cobra's than new Soviet aricrafts until the end of the war - like Alexander Pokryshkin, three times Hero of the Soviet Union with 53 kills. Reliability.

 

But it  would be obviously too frustrating to fly Soviet side if we would implement such things, so we need to find some compromise.

What is now it is not really a fair compromise and the changes went too far in the opposite direction: it's just a fight between perfect quality pre-production prototypes on the Russian side against some severly used line German airplanes at the very end of their resurs/life cycle.

 

I'm aware my La-5 if far better then real La-5 on which Soviet pilots were forced to fly IRL so i don't need to unrealistically castrate the opponents even more.

It should look like in history: at the first half of the war Soviet pilots should fight heroically against vastly superior opponent, being at disadvantage in spite of numerical advantage over Germans and with the progress of the war they would caught up.

 

Even this 3 minute mark for 1.42ATA/2700 which was used in real Bf-109F4 as shown in photos had some safety margin and the catastrophic failure of an engine wouldn't happened before about 5-6 minutes. This one minute which is in the game right now was obviously just the request for pilots in their manual to save engine resurs and had nothing to do with real engine limitation

 

So stay positive because it is - anyway - by far THE BEST WWII sim created to this date and we should focus on developement and improvement of this Great game.

 

cheers

Edited February 20, 2018 by Bies